In the last few years, a growing interest has been shown in the development of new pyrrolo[2,1-c][1,4]benzodiazepines (PBDs). These antibiotics react covalently with DNA to form an N2-guanine adduct that lies within the minor groove of duplex DNA via an acid-labile aminal bond to the electrophilic imine at the N10-C11 position. (Ref. Kunimoto, S.; Masuda, T.; Kanbayashi, N.; Hamada, M.; Naganawa, H.; Miyamoto, M.; Takeuchi, T. and Unezawa, H. J. Antibiot. 1980, 33, 665.; Kohn, K. W. and Speous, C. L. J. Mol. Biol. 1970, 51, 551.; Hurley, L. H.; Gairpla, C. and Zmijewski, M. Biochem. Biophys. Act. 1977, 475, 521.; Kaplan, D. J. and Hurley, L. H. Biochmestry 1981, 20, 7572). The molecules have a right-handed twist which allows them to follow the curvature of the minor groove of B-form double-stranded DNA spanning three base pairs. A recent development has been the linking of two PBD units through their C 8 positions to give bisfunctional alkylating agents capable of cross-linking DNA (Ref: Thurston, D. E.; Bose, D. S.; Thomson, A. S.; Howard, P. W.; Leoni, A.; Croker, S. J.; Jenkins, T. C.; Neidle, S. and Hurley, L. H. J. Org. Chem. 1996, 61, 8141-8147). Recently, a non-cross-linking mixed imine-amide PBD dimers have been synthesized that have significant DNA binding ability and potent anti tumour activitiy (Kamal, A.; Laxman, N.; Ramesh, G.; Ramulu, P and Srinivas, O. U.S. Pat. No. 636,233. dt 26-Mar.-2002.; Kamal, A.; Ramesh, G.; Laxman, N.; Ramulu, P.; Srinivas, O.; Neelima, K.; Kondapi, A. K.; Srinu, V. B.; Nagarajaram, H. M. J. Med. Chem. 2002, 45, 4679).
Naturally occurring pyrrolo[2,1-c][1,4]benzodiazepines belongs to a group of antitumour antibiotics derived from Streptomyces species. Recently, there is much impetus for the PBD systems as they can recognize and bind to specific sequence of DNA. Examples of naturally occurring PBD's include anthramycin, DC-81, tomaymycin, sibiromycin and neothramycin.
However, the clinical efficacy for these antibiotics is hindered by several limitations, such as poor water solubility, cardiotoxicity and metabolic inactivation.
The compounds of present invention has a difference with C-8 linked secondary amine congeners by the replacement of phenolic hydrogen of (11aS)-8-Hydroxy-7-methoxy-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine-5-one (DC-81).
Pyrrolo[2,1-c][1,4]benzodiazepine-5-ones are a class of compounds that bind to DNA by non-covalent interactions such as hydrophobic, Vanderwaal's interactions and hydrogen bonding between ring substituents and DNA, are also responsible for the influence on the sequence selectivity.